Masseter muscle rigidity and malignant hyperthermia susceptibility in pediatric patients. An update on management and diagnosis.

BACKGROUND: Controversy exists regarding the definition of masseter muscle rigidity (MMR) and anesthetic management after MMR. This study reports current anesthetic management after MMR, estimates the incidence of clinical malignant hyperthermia (MH) in patients with MMR, and is the first to evaluate the coincidence of MMR with malignant hyperthermia susceptibility (MHS) according to the 1987 North American Malignant Hyperthermia Group protocol. METHODS: Practicing anesthesiologists referred pediatric patients for biopsy between 1986 and 1991 based on evidence of MMR after succinylcholine (1975-1991). The clinical scenario was described as MMR alone or MMR followed by signs of MH, including arterial CO2 tension > 50 mmHg, arterial pH < or = 7.25, and base deficit > 8. Patients had caffeine-halothane muscle contracture testing to determine MHS. RESULTS: Seventy patients (50 boys and 20 girls) were evaluated. Eighty-three percent (58 of 70) of anesthetics were halothane-succinylcholine. In 68% (48 of 70) of cases, the anesthetic was discontinued, whereas anesthesia was continued with nontriggering agents in 11% (8 of 70) and with triggering agents in 13% (9 of 70). Fifty-nine percent (41 of 70) of patients were diagnosed as MHS by muscle biopsy. In 7% (5 of 70) of patients, clinical MH developed within 10 min of MMR. CONCLUSIONS: This study, by using the current North American Malignant Hyperthermia Group protocol, reaffirms the high incidence (59%, 41 of 70) of MHS associated with MMR as confirmed by muscle biopsy. Of the MHS patients, 5 developed signs of clinical MH. Most anesthesiologists in this study, when confronted with MMR, discontinued anesthesia. Because of the potential lethality of MH and the > 50% concordance between MMR and MHS, the most conservative course of action after MMR is to discontinue the anesthetic and observe the patient for clinical evidence of MH. An acceptable alternative, depending on the urgency of the surgery, would be to continue anesthesia with nontriggering agents for MH, with appropriate monitoring.

Evidence for genetic heterogeneity in malignant hyperthermia susceptibility.

Malignant hyperthermia susceptibility (MHS) is a clinically heterogeneous pharmacogenetic disorder characterized by accelerated metabolism, hyperthermia, and frequently muscle rigidity. MHS is elicited by all commonly used potent inhalation anesthetics and depolarizing neuromuscular blockers and remains an important cause of death due to anesthesia. Recent linkage studies suggest a single genetic locus for this disorder on chromosome 19q13.1. The results of our linkage analyses exclude several loci on 19q13.1 as a site for the gene(s) that produces the MHS phenotype in three unrelated families and clearly establish genetic heterogeneity in this disorder. These results are consistent with the hypothesis that the genetic defect that alters thermoregulation may vary in MHS and that clinical variability in the expression of MHS may be explained by genetic heterogeneity.

Cleft palate lateral synechia syndrome. Review of the literature and case report.

Cleft palate lateral synechiae syndrome is a rare syndrome consisting of cord-like interalveolar adhesions and concomitant hypoplasia of the mandible. We have presented an infant with CPLS syndrome and coincident hydrocephalus. Surgical division of the adhesions is necessary to allow normal feeding, avoid upper airway obstruction, and allow normal mandibular function and growth.

Peripherally inserted central venous catheters for treatment of cystic fibrosis.

Patients who have cystic fibrosis (CF) are frequently hospitalized for long-term intravenous (IV) treatment. We evaluated clinical effectiveness of the Drum-Cartridge Catheter (Abbott Laboratories) for such patients. The catheter is placed peripherally under local anesthesia via an antecubital vein into the superior vena cava or right atrium. Patients who were more than 10 years of age and who were hospitalized for IV antibiotic therapy and/or IV hyperalimentation were studied. All but 2 patients had CF. Using an aseptic technique the catheters were inserted into the basilic or cephalic vein. Chest radiographs were used to confirm the final location of the catheter. Catheters were used to administer IV antibiotics, hyperalimentation, and lipids. There were 38 catheterizations in 23 patients; several patients had repeated insertions at later admissions. The success rate of insertion was 86% with 31 of the 38 insertions initially located either in the superior vena cava or right atrium. Mean duration of catheterization was 15.4 days (range 5-49 days). No major complications such as sepsis, catheter or clot embolism, pneumothorax, vascular perforation, or hemorrhage occurred in the patients who had DF. Complications that required displacement of catheter into the axillary vein (1 patient), and cracked catheter hub (1 patient). This study shows that the Drum-Cartridge Catheter can be used easily for IV therapy of patients who have CF for a long duration, repeatedly, and with no major complications.

A newly recognized profile in neonatal lung disease with maternal diabetes.

A radiographic pattern associated with respiratory distress, distinct from hyaline membrane disease and transient tachypnea of the newborn, is described in eight infants of diabetic mothers. The radiographic findings demonstrate a regional distribution of reticulogranular densities accompanied by increased lung volumes. Clinical features were gestationally mature infants in moderate respiratory distress with tachypnea, hypercapnia, and hypoxemia requiring supplemental oxygen, with steady improvement and uneventful recovery within 2 weeks. There was no bacteriologic evidence of infection or radiographic evidence of delayed lung fluid absorption. The mothers had mild diabetes. These features characterize a newly recognized entity in diabetes-related idiopathic lung disease of the newborn. Possible causative factors are discussed.

Inappropriate secretion of antidiuretic hormone in a postsurgical pediatric population.

Twenty-four pediatric patients undergoing corrective posterior spinal fusion surgery for idiopathic scoliosis were studied to determine the frequency with which the syndrome of inappropriate antidiuretic hormone secretion (SIADH) developed. We measured arterial blood gases, serum and urine electrolytes and osmolalities, CVP, and urine output during and after surgery. The 20 patients receiving hypotonic iv salt solution in the immediate postoperative period experienced a significant drop in serum sodium values (6.2 +/- 2.9 mEq/L) and 5 (25%) developed SIADH as diagnosed by routine laboratory procedures. Four patients were treated with iv isotonic salt solution. No patient developed hyponatremia (serum Na+ less than 130 mEq/L) and the decrease in serum sodium (3.0 +/- 0.8 mEq/L) was not statistically significant. We conclude that SIADH occurs commonly in patients undergoing corrective vertebral surgery and that vigilant attention must be paid to their fluid and electrolyte management in the postoperative period.

Use of external expiratory resistance in intubated neonates to increase lung volume.

Ten intubated neonates (weights 0.90 to 2.58 kg) recovering from respiratory disease had lung mechanics, respiratory patterns, and functional residual capacity measured at 0 cmH2O continuous positive airways pressure and then after application of serially increasing levels of external expiratory resistance. At an external expiratory resistance greater than 40 cmH2O/1 per second, there was a significant increase in mean functional residual capacity compared with control levels. Immediately after the application of external expiratory resistance, there was a significant decrease in flow which returned to control values after a few breaths. Tidal volume and respiratory rate decreased for a few breaths after the application of the external expiratory resistance, but returned to control values after several seconds. Study age, gestational age, or study weight had no appreciable effect on the relationship between functional residual capacity and external expiratory resistance. Application of external expiratory resistance may be useful for stabilising lung volume in neonates recovering from respiratory disease.

The effect of external expiratory resistance on lung volume and pulmonary function in the neonate.

To investigate the acute physiologic effects of external expiratory resistance on lung function in extubated neonates recovering from respiratory disease, lung mechanics, respiratory patterns, and functional residual capacity were measured in ten neonates dueing a control period and immediately after application of an external expiratory resistance of 30 cm H2O/l/second via a face mask. Following application of EER, mean FRC increased by 40.8% (P less than 0.05). The work of breathing was significantly increased after the EER was applied; there was also a significant increase in measured expiratory resistance and a decrease in inspiratory-expiratory time ratio. The change in lung volume was rapid, requiring less than five seconds for the new end-expiratory level to be reached. Dynamic lung compliance, inspiratory resistance, and respiratory rate did not change during any phase of the study. The application of external expiratory resistance may have potential therapeutic value by increasing lung volume in infants recovering from respiratory disease.

A clinical score for predicting the level of respiratory care in infants with respiratory distress syndrome.

A scoring system was developed to predict the need for transferring infants with respiratory distress syndrome (RDS) from community hospitals to specialized respiratory care centers. Five clinical and laboratory determinations (birthweight, clinical RDS score, FI02, PCO2 and pH) recorded from 100 infants with RDS during one year were utilized in a score with values ranging from 0 to 10. Application of the score to 159 infants with RDS during the following year showed that: (1) 73 per cent of infants scoring less than or equal to 3 received only oxygen by hood; (2) 75 per cent of infants scoring 4--5 required continuous positive airway pressure (CPAP); and (3) 87 per cent of infants scoring greater than or equal to 6 needed mechanical ventilation (7V). Mean scores were significantly different (p less than 0.02) for each type of respiratory therapy employed: oxygen by hood (2.30 +/- 0.19 S.E.M.); CPAP (4.27 +/- 0.16 S.E.M.); MV (6.72 +/- 0.25 S.E.M.). The accuracy and simplicity of the score make it valuable for the physician in the community hospital to assist in deciding when to transfer a neonate with RDS for more intensive respiratory therapy.

Improved oxygenation and lung compliance with prone positioning of neonates.

Fourteen intubated infants recovering from neonatal respiratory disease had arterial blood gases and lung mechanics measured in the supine position and in two variants of the prone position. Prone positioning resulted in significant increases in mean (+/- SEM) arterial oxygen tension (Pa(o2 70.4 +/- 2.5 to 81.1 +/- 4.4mm Hg), dynamic lung compliance (1.7 +/- 0.24 to 2.55 +/- 0.37 ml/cm H2O),and tidal volume (8.6 +/- 1.0 to 10.5 +/- 1.2 ml) when all prone values were compared to supine values. Prone positioning with the abdomen protruding freely, when compared to all supine values, was associated with significantly increased dynamic lung compliance and tidal volume. Values for prone-abdomen free were not significantly different from values for prone-abdomen restricted. This suggests that there are clinical benefits from prone positioning in neonates recovering from respiratory disease.

A new device for diagnosis and treatment of neonatal pneumothorax.

A new closed-system device for the diagnosis and treatment of pneumothorax was evaluated in ten New Zealand white rabbits and compared with and open-system needle. The closed-system device proved to be safe for diagnostic thoracentesis. There were no pneumothoraces as a result of the procedure with the closed-system device as confirmed by chest roentgenograms and pleural pressure measurements. In contrast, 70% of the diagnostic thoracenteses with the open-system needle were associated with pneumothorax documented by x-ray films and a significant increase in mean pleural pressure. The new apparatus was more efficacious for evacuation of pneumothoraces because complete air removal occurred in 90% of the rabbits as compared with 60% of trials with the open-system needle. If the efficacy of the new closed-system device proves to be good in human infants, the pediatrician encountering a tension pneumothorax in the newborn can use a completely assembled system that is safe for diagnosing and treating this acute life-threatening condition.